医用高分子材料在医疗器械中的应用

本文论述了医用高分子材料的发展概况，主要介绍了聚氯酯、聚氯乙烯、硅橡胶材料的特性及其在医疗器械中的应用。     

Central scotoma associated with intraocular silicone oil tamponade develops before oil removal

Background Unexplained sudden visual loss after removal of silicone oil from the eye has recently been described. We report the occurrence and features of unexplained central scotoma developing with silicone oil in situ in the vitreous cavity. Methods A retrospective case series of five patients (from two centres) who reported a central scotoma commencing during silicone oil tamponade was studied. All patients had vitrectomy for macula-on retinal detachment, with ultra-purified silicone oil tamponade (four out of five had giant retinal tear). Investigations included visual acuity, intraocular pressure, optical coherence tomography, fluorescein angiography, visual fields and electrophysiology. Results All patients reported a central scotoma that appeared during oil tamponade. Visual acuity fell by a mean of 0.93 LogMAR units after onset of the scotoma. After cataract extraction and oil removal, vision remained reduced by a mean of 0.8 units. The mean duration of oil in the eye was 2.7 months when the scotoma was noted by the patient. Investigations were performed after removal of oil. Fluorescein angiography (FFA) was performed in two cases and optical coherence tomography (OCT) in five patients. No abnormality was demonstrated. Electrophysiology was performed in five patients with pattern electroretinography suggestive of macular dysfunction in four patients. Conclusion This is the first case series describing central scotoma associated with silicone oil in situ. Electrophysiology indicated macular dysfunction in most cases. We suggest that early removal of oil in cases with good visual potential should be considered to avoid this sight-threatening complication. Presented in part at Britain and Eire Association of Vitreo-Retinal Surgeons, November 2003.     

Long-term histological response to intravenous Teflon and silicone in a rat model

Particle migration is one of the main concerns raised when implanted plastics are discussed, especially when used for the endoscopic treatment of vesicoureteric reflux in children. To study the histological response to migrated plastic material, we injected particulate plastics (Teflon and silicone) into the jugular vein of 21 Sprague-Dawley rats, 11 of which were killed at 12 months, 9 at 2 years, and 1 died at 18 months. The findings were similar for Teflon and silicone and unchanged after from 1 to 2 years. The plastic particles were seen outside pulmonary vessels, within aggregated multinucleate giant cells, surrounded by only small numbers of other types of inflammatory cells.     

Microscopic polyangiitis after silicone breast implantation

We describe the case of a patient who developed microscopic polyangiitis (MPA) after silicone breast implantation. A 60-year-old woman who had undergone silicone breast implantation was admitted to our hospital with complaints of general malaise and hematoproteinuria. She was diagnosed as having MPA with evidence of acute progressive renal failure, pulmonary hemorrhage, and positivity for myeloperoxidase-antineutrophil cytoplasmic antibody (ANCA). A renal biopsy showed severe necrotizing and crescentic glomerulonephritis with arteriolitis. The patient received high-dose steroids and plasma exchange treatment, but died of progressive pulmonary hemorrhage and multiple cerebral hemorrhage. Silicone implantation is associated with scleroderma, systemic lupus erythematosus, and rheumatoid arthritis. This case report indicates the possibility of the development of MPA after silicone breast implantation.     

Sudden onset breast swelling: an unusual presentation of ruptured prosthesis 10 years post-implantation

Silicone-gel breast implants are widely used throughout the world for breast augmentation and reconstruction, and complications associated with long-term in vivo presence are well reported, particularly in relation to implant rupture. We report an unusual and atypical clinical presentation of large intracapsular seroma formation, not previously reported with silicone-gel breast prosthesis rupture.     

Blue rubber-bleb nevus syndrome: report of a case associated with osteoid osteomas

Blue rubber-bleb nevus syndrome (BRBNS), or Bean's syndrome, is a rare angiomatosis characterized by multiple cavernous hemangiomas of the skin, mucosae and frequently of other sites. A 49-year-old male patient had been affected since birth by multiple angiomas localized in the skin, lips, oral cavity, cranial theca, and central nervous system; intrauterine rupture of angiomas in the right parietal lobe had caused partial hypotrophic paralysis of the left hemisoma. In addition to BRBNS, the patient was affected by three osteoid osteomas: this never-described clinical association is here discussed.     

Comparison of a new heparin-coated dense membrane lung with nonheparin-coated dense membrane lung for prolonged extracorporeal lung assist in goats

Thrombosis and bleeding are major complications in cases of prolonged extracorporeal lung assist (ECLA) with an artificial-membrane lung. Antithrombogenic treatment of the artificial-membrane oxygenator and circuits is indispensable for safe ECLA. The efficacy of a new heparin-coated membrane lung with minimal systemic heparinization was evaluated for 7 days and compared with a nonheparin-coated membrane lung in goats. The animals were randomly assigned to either the heparin-coated membrane group (HM group, n = 5) or nonheparin-coated membrane group (NHM group, n = 5). Activated coagulation time (ACT) during ECLA was controlled to below 150 s in the HM group, and to near 200 s in the NHM group. All goats in the HM group were sustained on ECLA for 7 days, but two goats in the NHM group died on the 4th and 6th days, respectively. The mean systemic administration rate of heparin during ECLA was 22.4 +/- 4.4 U/kg/h in the HM group and 39.0 +/- 10.0 U/kg/h in the NHM group. There was a significant difference between the two groups (P < 0.05). The oxygen transfer rate, the Pco(2) difference, the perfusion resistance, and platelet counts showed no significant changes. There was no plasma leakage from the artificial lung. Although several clots were observed in the stagnant areas of the artificial lung, they did not lead to deterioration of the function of the artificial lung. The excellent antithrombogenicity, gas exchange ability, and durability of this new artificial lung with circuits might contribute to successful prolonged ECLA with minimal systemic heparinization.     

Development of silicone rubber hollow fiber membrane oxygenator for ECMO

Silicone rubber hollow fiber membrane produces an ideal gas exchange for long-term ECMO due to nonporous characteristics. The extracapillary type silicone rubber ECMO oxygenator having an ultrathin hollow fiber membrane was developed for pediatric application. The test modules were compared to conventional silicone coil-type ECMO modules. In vitro experiments demonstrated a higher O2 and CO2 transfer rate, lower blood flow resistance, and less hemolysis than the conventional silicone coil-type modules. This oxygenator was combined with the Gyro C1E3 centrifugal pump, and three ex vivo experiments were conducted to simulate pediatric V-A ECMO condition. Four day and 6 day experiments were conducted in cases 1 and 2, respectively. Case 3 was a long-term experiment up to 2 weeks. No plasma leakage and stable gas performances were achieved. The plasma free hemoglobin was maintained within a normal range. This compact pump-oxygenator system in conjunction with the Gyro C1E3 centrifugal pump has potential for a hybrid total ECMO system.